Substituent and solvent effects on the rate of the reaction of 2-methyl-4-phenyl-thiazole ethiodide with substituted benzaldehydes

Condensation of 2-methyl-4-phenyl-thiazole ethiodide (1) with aromatic aldehydes in presence of piperidine as base catalyst has been studied kinetically at different temperatures. The rate in presence of low concentration of piperidine (<0.5M) is found to be represented by the third order equationv=k [1] [aldehyde] [piperidine]. On the other hand the rate in presence of 1.013M piperidine is represented by the second-order equation:v=k [1] [aldehyde]. It is concluded from the kinetic results that the dehydration step of the intermediate aldol compound is the rate determining step of the reaction. The dependence of the mechanism of the reaction and the thermodynamic parameters of activation on the molecular structure of the various aromatic aldehydes used is discussed. In various organic solvents, the rate of the reaction increases as the dielectric constant of the medium is increased. The energy of activation and the thermodynamic parameters of activation were calculated and discussed in terms of solvent properties.

---

Substituenten- und Lösungsmittel-Effekte auf die Geschwindigkeit der Reaktion zwischen 2-Methyl-4-phenylthiazol-ethiodid und substituierten Benzaldehyden

Zusammenfassung Die Kinetik dieser Kondensation wurde bei verschiedenen Piperidinkonzentrationen (basischer Katalysator), unter Variation der Temperatur und in Abhängigkeit von der Polarität des Lösungsmittels für verschiedene substituierte Benzaldehyde untersucht. Bei niedriger Piperidinkonzentration gehorcht die Reaktion einer Gleichung dritter Ordnung:v=k [Thiazo] [Ald.] [Pip.]; bei großer Konzentration (1.013M) gilt eine Gleichung zweiter Ordnung:v=k [Thizol] [Ald.]. Es wird ein Mechanismus vorgeschlagen, wobei der geschwindigkeitsbestimmende Schritt die Dehydratisierung des intermediär gebildeten Aldols ist. Aktivierungsenergien und andere thermodynamische Parameter wurden bestimmt und im Hinblick auf die Lösungsmittelpolarität diskutiert.

     

31P chemical shifts in N-aryliminotriphenylphosphoranes

³¹P chemical shifts in N-aryliminotriphenylphosphoranes and the corresponding N-methylated phosphonium salts are presented. They can be correlated with those theories of the bonding in phosphorus-nitrogen ylides which involve partial double bonding as a result of p^π–d^π overlap.     

Field distribution in a fabry-perot interferometer with inclined mirrors

The field is localized in planes perpendicular to the principal section of the wedge formed by the mirrors; the positions of these are defined by Airy's function, with secondary components accessible to observation.I am indebted to Professor F. A. Korolev for discussions.     

Effects of polymer–fiber interactions on rheology and flow behavior of suspensions of semi-flexible fibers in polymeric liquids

Rheological properties of suspensions of fibers in polymeric fluids are influenced by fiber–polymer interactions. In this paper, we investigate this influence from both experimental and modeling standpoints. In the experimental part of this investigation, we have changed the fiber–polymer interactions by treating the surface of the fibers. The resulting effects are observed using scanning electron microscopy and dynamic mechanical analysis techniques and quantified from the measurements of the viscosity in the start-up of shear flows and dynamic tests in the linear viscoelastic range region. The results are interpreted with the help of a mesoscopic rheological model developed for suspensions of fibers in viscoelastic fluids.     

Template synthesis and spectroscopic studies of highly conjugated tetraiminetetraamide macrocyclic complexes from 1,2-diphenylethane-1,2-dione dihydrazone

A new class of tetraiminetetraamide macrocyclic (Ph4[20]tetraene, N8O4, and Ph6[20]tetraene, N8O4) complexes have been prepared through the metal ion controlled reaction of 1,2-diphenylethane-1,2-dione dihydrazone (DPEDDH) with succinic acid [ML1X2] or phthalic acid [ML2X2] [M=Mn, Co, Ni, Cu or Zn; X=Cl or NO3]. The structures of the complexes have been elucidated on the basis of i.r, 1H-n.m.r, e.p.r. and electronic spectral data and conductance, as well as magnetic, properties. An octahedral geometry is assigned for all the complexes, involving coordination of the all-imine nitrogens.     

Complexes of vitamin B6 XII : Mixed ligand complexes of some divalent metal ions with pyridoxamine and histidine

Potentiometric pH titrations (I = 0.15 M NaNO₃; 37°C) have been employed to study the various complex equlibria in the systems involving pyridoxamine and histidine with Co(II), Ni(II), Cu(II), and Zn(II). The stoichiometry and formation constants of different species have been determined with the aid of MINIQUAD-75. The complexes obtained were mostly protonated and positively charged. The formation of the ternary species is discussed in terms of the binary species. They were also correlated with the quaternary species involving pyridoxamine, glycine, and imidazole. Spectral analysis of the complex solutions of different compositions are also reported. The relevance of these ternary complex equilibria to some biological functions is discussed.     

Structural characterization of polybenzyls by high field 13C-NMR spectroscopy

¹³C-NMR Spectroscopy has been used for the structural characterization of polybenzyls synthesized from the polymerization of benzyl chloride catalyzed by arene chromium tricarbonyls. The ¹³C-chemical shifts for various mono-, di-, tri-, and tetrasubstituted phenyl groups in a polybenzyl have been calculated by the use of additivity parameters and compared with their observed shifts. Although from a theroetical point of view, polysubstitution on a phenyl ring gives rise to a number of isomers, the results indicate the preferential formation of only a few of them due to steric and electronic considerations. Based on quantitative ¹³C-NMR data, several important structural parameters including the percentage of mono-, di-, tri-, and tetrasubstituted phenyl rings in the polybenzyl can be calculated. The extent of branching in a number of polybenzyls prepared under different experimental conditions was determined. The results indicate an increase in branching with the increase in reaction temperature.     

Activated nitriles in heterocyclic synthesis. Part III. Synthesis of N-amino-2-pyridone,pyranopyrazole and thiazolopyridine derivatives

The reaction of 2-cyanoethanoic acid hydrazide and arylidenemalononitrile was studied as a new route for the synthesis of N-amino-2-pyridones. Pyrano[2,3-c]pyrazole and thiazolo[2,3-a]pyridine could be prepared from the reaction of arylideneazolones with the same reagent.